Aisah A. Aubdool

Neurovascular aspects of skin neurogenic inflammation.

Neurogenic inflammation is involved in skin inflammation. It is hypothesized that it is involved in the pathogenesis of the common chronic cutaneous vascular disorder rosacea, but the exact mechanism of action is currently unknown. Transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) are widely expressed on primary sensory neuron endings and non-neuronal cells such as keratinocytes. Here we describe the potential for TRPV1 and TRPA1 receptors to be involved in the pathophysiology of rosacea due to their polymodal activation, including cold and hot temperature, pungent products from vegetable and spices, reactive oxygen species, and mechanical stimuli. We discuss the role of both receptors and the sensory neuropeptides that they release in inflammation and pain sensation and evidence suggesting that both TRPV1 and TRPA1 receptors may be promising therapeutic targets for the treatment of the inflammatory symptoms of rosacea.

4-Oxo-2-nonenal (4-ONE): Evidence of Transient Receptor Potential Ankyrin 1-Dependent and -Independent Nociceptive and Vasoactive Responses In Vivo

This study explores the in vivo effects of the proposed transient receptor potential ankyrin 1 (TRPA1) agonist 4-oxo-2-nonenal (4-ONE). Pharmacological inhibitors and genetically modified mice were used to investigate the ability of 4-ONE to act via TRPA1 receptors and possible mechanisms involving transient receptor potential vanilloid 1 (TRPV1). We hypothesized that 4-ONE activates sensory nerves, via TRPA1 or possibly TRPV1, and thus triggers mechanical hyperalgesia, edema formation, and vasodilatation in mice. An automated dynamic plantar aesthesiometer was used to determine hind paw withdrawal thresholds, and a laser Doppler flowmeter was used to measure skin blood flow. Edema formation was determined by measuring paw weights and thickness. 4-ONE (10 nmol) triggers unilateral mechanical hyperalgesia, edema formation, and vasodilatation in mice and is shown here to exhibit TRPA1-dependent and -independent effects. Neurogenic vasodilatation and mechanical hyperalgesia at 0.5 h postinjection were significantly greater in TRPA1 wild-type (WT) mice compared with TRPA1 knockout (KO) mice. Edema formation throughout the time course as well as mechanical hyperalgesia from 1 to 4 h postinjection were similar in WT and TRPA1 KO mice. Studies involving TRPV1 KO mice revealed no evidence of TRPV1 involvement or interactions between TRPA1 and TRPV1 in mediating the in vivo effects of 4-ONE. Previously, 4-ONE was shown to be a potent TRPA1 agonist in vitro. We demonstrate its ability to mediate vasodilatation and certain nociceptive effects in vivo. These data indicate the potential of TRPA1 as an oxidant sensor for vasodilator responses in vivo. However, 4-ONE also triggers TRPA1-independent effects that relate to edema formation and pain.

TRPA1 is essential for the vascular response to environmental cold exposure

The cold-induced vascular response, consisting of vasoconstriction followed by vasodilatation, is critical for protecting the cutaneous tissues against cold injury. Whilst this physiological reflex response is historic knowledge, the mechanisms involved are unclear. Here by using a murine model of local environmental cold exposure, we show that TRPA1 acts as a primary vascular cold sensor, as determined through TRPA1 pharmacological antagonism or gene deletion. The initial cold-induced vasoconstriction is mediated via TRPA1-dependent superoxide production that stimulates α2C-adrenoceptors and Rho-kinase-mediated MLC phosphorylation, downstream of TRPA1 activation. The subsequent restorative blood flow component is also dependent on TRPA1 activation being mediated by sensory nerve-derived dilator neuropeptides CGRP and substance P, and also nNOS-derived NO. The results allow a new understanding of the importance of TRPA1 in cold exposure and provide impetus for further research into developing therapeutic agents aimed at the local protection of the skin in disease and adverse climates.

Superoxide generation and leukocyte accumulation: key elements in the mediation of leukotriene B4-induced itch by transient receptor potential ankyrin 1 and transient receptor potential vanilloid 1

The underlying mechanisms of itch are poorly understood. We have investigated a model involving the chemoattractant leukotriene B4 (LTB4) that is up‐regulated in common skin diseases. Intradermal injection of LTB4 (0.1 nmol/site) into female CD1 mice induced significant scratching movements (used as an itch index) compared with vehicle‐injected (0.1% bovine serum albumin‐saline) mice. Intraperitoneal transient receptor potential (TRP) channel antagonist treatment significantly inhibited itch as follows: TRP vanilloid 1 (TRPV1) antagonist SB366791 (0.5 mg/kg, by 97%) and the TRP ankyrin 1 (TRPA1) antagonists TCS 5861528 (10 mg/kg; 82%) and HC‐030031 (100 mg/kg; 76%). Leukotriene B4 receptor 2 antagonism by LY255283 (5 mg/kg i.p.; 62%) reduced itch. Neither TRPV1‐knockout (TRPV1‐KO) nor TRPA1‐knockout (TRPA1‐KO mice exhibited LTB4‐induced itch compared with their wild‐type counterparts. The reactive oxygen species scavengers N‐acetylcysteine (NAC; 204 mg/kg i.p.; 86%) or superoxide dismutase (SOD; 10 mg/kg i.p.; 83%) also inhibited itch. LTB4‐induced superoxide release was attenuated by TCS 5861528 (56%) and HC‐030031 (66%), NAC (58%), SOD (50%), and LY255283 (59%) but not by the leukotriene B4 receptor 1 antagonist U‐75302 (9 nmol/site) or SB366791. Itch, superoxide, and myeloperoxidase generation were inhibited by the leukocyte migration inhibitor fucoidan (10 mg/kg i.v.) by 80, 61, and 34%, respectively. Myeloperoxidase activity was also reduced by SB366791 (35%) and SOD (28%). TRPV1‐KO mice showed impaired myeloperoxidase release, whereas TRPA1‐KO mice exhibited diminished production of superoxide. This result provides novel evidence that TRPA1 and TRPV1 contribute to itch via distinct mechanisms.—Fernandes, E. S., Vong, C. T., Quek, S., Cheong, J., Awal, S., Gentry, C., Aubdool, A. A., Liang, L., Bodkin, J.V., Bevan, S., Heads, R., Brain, S.D. Superoxide generation and leukocyte accumulation: key elements in the mediation of leukotriene B4‐induced itch by transient receptor potential ankyrin 1 and transient receptor potential vanilloid 1. FASEB J. 27, 1664–1673 (2013). www.fasebj.org

4-oxo-2-nonenal (4-ONE): Evidence of TRPA1-dependent and - independent nociceptive and vasoactive responses in vivo.

This study explores the in vivo effects of the proposed transient receptor potential ankyrin 1 (TRPA1) agonist 4-oxo-2-nonenal (4-ONE). Pharmacological inhibitors and genetically modified mice were used to investigate the ability of 4-ONE to act via TRPA1 receptors and possible mechanisms involving transient receptor potential vanilloid 1 (TRPV1). We hypothesized that 4-ONE activates sensory nerves, via TRPA1 or possibly TRPV1, and thus triggers mechanical hyperalgesia, edema formation, and vasodilatation in mice. An automated dynamic plantar aesthesiometer was used to determine hind paw withdrawal thresholds, and a laser Doppler flowmeter was used to measure skin blood flow. Edema formation was determined by measuring paw weights and thickness. 4-ONE (10 nmol) triggers unilateral mechanical hyperalgesia, edema formation, and vasodilatation in mice and is shown here to exhibit TRPA1-dependent and -independent effects. Neurogenic vasodilatation and mechanical hyperalgesia at 0.5 h postinjection were significantly greater in TRPA1 wild-type (WT) mice compared with TRPA1 knockout (KO) mice. Edema formation throughout the time course as well as mechanical hyperalgesia from 1 to 4 h postinjection were similar in WT and TRPA1 KO mice. Studies involving TRPV1 KO mice revealed no evidence of TRPV1 involvement or interactions between TRPA1 and TRPV1 in mediating the in vivo effects of 4-ONE. Previously, 4-ONE was shown to be a potent TRPA1 agonist in vitro. We demonstrate its ability to mediate vasodilatation and certain nociceptive effects in vivo. These data indicate the potential of TRPA1 as an oxidant sensor for vasodilator responses in vivo. However, 4-ONE also triggers TRPA1-independent effects that relate to edema formation and pain.

Cardioprotective effects of Cu((II))ATSM in human vascular smooth muscle cells and cardiomyocytes mediated by Nrf2 and DJ-1.

Cu(II)ATSM was developed as a hypoxia sensitive positron emission tomography agent. Recent reports have highlighted the neuroprotective properties of Cu(II)ATSM, yet there are no reports that it confers cardioprotection. We demonstrate that Cu(II)ATSM activates the redox-sensitive transcription factor Nrf2 in human coronary artery smooth muscle cells (HCASMC) and cardiac myocytes (HCM), leading to upregulation of antioxidant defense enzymes. Oral delivery of Cu(II)ATSM in mice induced expression of the Nrf2-regulated enzymes in the heart and aorta. In HCASMC, Cu(II)ATSM increased expression of the Nrf2 stabilizer DJ-1, and knockdown of Nrf2 or DJ-1 attenuated Cu(II)ATSM-mediated heme oxygenase-1 and NADPH quinone oxidoreductase-1 induction. Pre-treatment of HCASMC with Cu(II)ATSM protected against the pro-oxidant effects of angiotensin II (Ang II) by attenuating superoxide generation, apoptosis, proliferation and increases in intracellular calcium. Notably, Cu(II)ATSM-mediated protection against Ang II-induced HCASMC apoptosis was diminished by Nrf2 knockdown. Acute treatment with Cu(II)ATSM enhanced the association of DJ-1 with superoxide dismutase-1 (SOD1), paralleled by significant increases in intracellular Cu(II) levels and SOD1 activity. We describe a novel mechanism by which Cu(II)ATSM induces Nrf2-regulated antioxidant enzymes and protects against Ang II-mediated HCASMC dysfunction via activation of the Nrf2/DJ-1 axis. Cu(II)ATSM may provide a therapeutic strategy for cardioprotection via upregulation of antioxidant defenses.

4α-phorbol 12,13-didecanoate activates cultured mouse dorsal root ganglia neurons independently of TRPV4

The Ca2+‐permeable cation channel TRPV4 is activated by mechanical disturbance of the cell membrane and is implicated in mechanical hyperalgesia. Nerve growth factor (NGF) is increased during inflammation and causes mechanical hyperalgesia. 4α‐phorbol 12,13‐didecanoate (4αPDD) has been described as a selective TRPV4 agonist. We investigated NGF‐induced hyperalgesia in TRPV4 wild‐type (+/+) and knockout (–/–) mice, and the increases in [Ca2+]i produced by 4αPDD in cultured mouse dorsal root ganglia neurons following exposure to NGF.

Design and pharmacological evaluation of PF-4840154, a non-electrophilic reference agonist of the TrpA1 channel.

TrpA1 is an ion channel involved in nociceptive and inflammatory pain. It is implicated in the detection of chemical irritants through covalent binding to a cysteine-rich intracellular region of the protein. While performing an HTS of the Pfizer chemical collection, a class of pyrimidines emerged as a non-reactive, non-covalently binding family of agonists of the rat and human TrpA1 channel. Given the issues identified with the reference agonist Mustard Oil (MO) in screening, a new, non-covalently binding agonist was optimized and proved to be a superior agent to MO for screening purposes. Compound 16a (PF-4840154) is a potent, selective agonist of the rat and human TrpA1 channel and elicited TrpA1-mediated nocifensive behaviour in mouse.

The sympathetic nervous system is controlled by transient receptor potential vanilloid 1 in the regulation of body temperature

Transient receptor potential vanilloid 1 (TRPV1) is involved in sensory nerve nociceptive signaling. Recently, it has been discovered that TRPV1 receptors also regulate basal body temperature in multiple species from mice to humans. In the present study, we investigated whether TRPV1 modulates basal sympathetic nervous system (SNS) activity. C57BL6/J wild‐type (WT) mice and TRPV1 knockout (KO) mice were implanted with radiotelemetry probes for measurement of core body temperature. AMG 9810∗∗∗ (50 mg/kg) or vehicle (2% DMSO/5% Tween 80/10 ml/kg saline) was injected intraperitoneally. Adrenoceptor antagonists or vehicle (5 ml/kg saline) was injected subcutaneously. In WT mice, the TRPV1 antagonist, AMG9810, caused significant hyperthermia, associated with increased noradrenaline concentrations in brown adipose tissue. The hyperthermia was significantly attenuated by the β‐adrenoceptor antagonist propranolol, the mixed α‐/β‐adrenoceptor antagonist labetalol, and the α1‐adrenoceptor antagonist prazosin. TRPV1 KO mice have a normal basal body temperature, indicative of developmental compensation. D‐Amphetamine (potent sympathomimetic) caused hyperthermia in WT mice, which was reduced in TRPV1 KO mice, suggesting a decreased sympathetic drive in KOs. This study provides new evidence that TRPV1 controls thermoregulation upstream of the SNS, providing a potential therapeutic target for sympathetic hyperactivity thermoregulatory disorders.—Alawi, K. M., Aubdool, A. A., Liang, L., Wilde, E., Vepa, A., Psefteli, M.‐P., Brain, S. D., Keeble, J. E. The sympathetic nervous system is controlled by transient receptor potential vanilloid 1 in the regulation of body temperature. FASEB J. 29, 4285‐4298 (2015). www.fasebj.org

A Novel α-Calcitonin Gene-Related Peptide Analogue Protects Against End-Organ Damage in Experimental Hypertension, Cardiac Hypertrophy and Heart Failure

Background: Research into the therapeutic potential of &agr;-calcitonin gene–related peptide (&agr;-CGRP) has been limited because of its peptide nature and short half-life. Here, we evaluate whether a novel potent and long-lasting (t½ ≥7 hours) acylated &agr;-CGRP analogue (&agr;Analogue) could alleviate and reverse cardiovascular disease in 2 distinct murine models of hypertension and heart failure in vivo. Methods: The ability of the &agr;Analogue to act selectively via the CGRP pathway was shown in skin by using a CGRP receptor antagonist. The effect of the &agr;Analogue on angiotensin II–induced hypertension was investigated over 14 days. Blood pressure was measured by radiotelemetry. The ability of the &agr;Analogue to modulate heart failure was studied in an abdominal aortic constriction model of murine cardiac hypertrophy and heart failure over 5 weeks. Extensive ex vivo analysis was performed via RNA analysis, Western blot, and histology. Results: The angiotensin II–induced hypertension was attenuated by cotreatment with the &agr;Analogue (50 nmol·kg–1·d–1, SC, at a dose selected for lack of long-term hypotensive effects at baseline). The &agr;Analogue protected against vascular, renal, and cardiac dysfunction, characterized by reduced hypertrophy and biomarkers of fibrosis, remodeling, inflammation, and oxidative stress. In a separate study, the &agr;Analogue reversed angiotensin II–induced hypertension and associated vascular and cardiac damage. The &agr;Analogue was effective over 5 weeks in a murine model of cardiac hypertrophy and heart failure. It preserved heart function, assessed by echocardiography, while protecting against adverse cardiac remodeling and apoptosis. Moreover, treatment with the &agr;Analogue was well tolerated with neither signs of desensitization nor behavioral changes. Conclusions: These findings, in 2 distinct models, provide the first evidence for the therapeutic potential of a stabilized &agr;Analogue, by mediating (1) antihypertensive effects, (2) attenuating cardiac remodeling, and (3) increasing angiogenesis and cell survival to protect against and limit damage associated with the progression of cardiovascular diseases. This indicates the therapeutic potential of the CGRP pathway and the possibility that this injectable CGRP analogue may be effective in cardiac disease.